Papers for Tuesday, Apr 02 2024

On 8 April 2024, tens of millions of people across North America will be able to view a total solar eclipse. Such astronomical events have been important throughout history, but with nearly 10,000 satellites in orbit, we question whether total eclipses will now reveal a sky full of satellites, fundamentally changing this experience for humanity. Using the current population of Starlink satellites, we find that the brightest satellites would be naked-eye visible in dark skies, but the high sky brightness during totality will make them undetectable to the unaided eye. Our model does not take into account the effects of chance reflections from large, flat surfaces like solar panels, which we expect will cause glints and flares that could be visible from large satellites and abandoned rocket bodies. Time-lapse all-sky imaging might reveal satellites during the eclipse.

The Space Domain Awareness (SDA) community routinely tracks satellites in orbit by fitting an orbital state to observations made by the Space Surveillance Network (SSN). In order to fit such orbits, an accurate model of the forces that are acting on the satellite is required. Over the past several decades, high-quality, physics-based models have been developed for satellite state estimation and propagation. These models are exceedingly good at estimating and propagating orbital states for non-maneuvering satellites; however, there are several classes of anomalous accelerations that a satellite might experience which are not well-modeled, such as satellites that use low-thrust electric propulsion to modify their orbit. Physics-Informed Neural Networks (PINNs) are a valuable tool for these classes of satellites as they combine physics models with Deep Neural Networks (DNNs), which are highly expressive and versatile function approximators. By combining a physics model with a DNN, the machine learning model need not learn astrodynamics, which results in more efficient and effective utilization of machine learning resources. This paper details the application of PINNs to estimate the orbital state and a continuous, low-amplitude anomalous acceleration profile for satellites. The PINN is trained to learn the unknown acceleration by minimizing the mean square error of observations. We evaluate the performance of pure physics models with PINNs in terms of their observation residuals and their propagation accuracy beyond the fit span of the observations. For a two-day simulation of a GEO satellite using an unmodeled acceleration profile on the order of $10^{-8} \text{ km/s}^2$, the PINN outperformed the best-fit physics model by orders of magnitude for both observation residuals (123 arcsec vs 1.00 arcsec) as well as propagation accuracy (3860 km vs 164 km after five days).

Line intensity mapping (LIM) has emerged as a promising tool for probing the 3D large-scale structure (LSS) through the aggregate emission of spectral lines. The presence of interloper lines poses a crucial challenge in extracting the signal from the target line in LIM. In this work, we introduce a novel method for LIM analysis that simultaneously extracts line signals from multiple spectral lines, utilizing the covariance of native LIM data elements defined in the spectral-angular space. We leverage correlated information from different lines to perform joint inference on all lines simultaneously, employing a Bayesian analysis framework. We present the formalism, demonstrate our technique with a mock survey setup resembling the SPHEREx deep field observation, and consider four spectral lines within the SPHEREx spectral coverage in the near infrared: H$\alpha$, $[$\ion{O}{3}$]$, H$\beta$, and $[$\ion{O}{2}$]$. We demonstrate that our method can extract the power spectrum of all four lines at $\gtrsim 10\sigma$ level at $z<2$. For the brightest line H$\alpha$, the $10\sigma$ sensitivity can be achieved out to $z\sim3$. Our technique offers a flexible framework for LIM analysis, enabling simultaneous inference of signals from multiple line emissions while accommodating diverse modeling constraints and parametrizations.

HD 21997 is host to a prototypical "hybrid" debris disk characterized by debris disk-like dust properties and a CO gas mass comparable to a protoplanetary disk. We use Transiting Exoplanet Survey Satellite time series photometry to demonstrate that HD 21997 is a high-frequency delta Scuti pulsator. If the mode identification can be unambiguously determined in future works, an asteroseismic age of HD 21997 may become feasible.

Mixed-morphology supernova remnants (MMSNRs) are characterized by a shell-like morphology in the radio and centrally-peaked thermal emission in the X-ray band. The nature of this peculiar class of supernova remnants (SNRs) remains a controversial issue. In this work, by pairing the predictions of stellar evolution theory with two-dimensional hydrodynamic simulations we show that the mixed morphology properties of a SNR can arise by the interaction of the SNR with the circumstellar medium shaped by a red supergiant progenitor star, embedded in a dense environment. As a study case, we model the circumstellar medium formation and the subsequent interaction of the SNR with it of a $15~\rm M_{\odot}$ progenitor star. The reflected shock, formed by the collision of the SNR with the density walls of the surrounding circumstellar cavity, accumulates and re-shocks the supernova ejecta at the center of the remnant, increasing its temperature so that the gas becomes X-ray bright. Such a formation mechanism may naturally explain the nature of MMSNRs resulted from Type II supernovae without the demand of additional physical mechanisms and/or ambient medium inhomogeneities. We discuss alternative evolutionary paths that potentially could be ascribed for the MMSNR formation within the framework of the reflected shock model.

Deep interferometric observations of CO and dust continuum emission are obtained with the Sub-Millimeter Array (SMA) at 230 GHz to investigate the physical nature of the giant molecular cloud (GMC) population in the Andromeda galaxy (M31). We use J = 2-1 $^{12}$CO and $^{13}$CO emission to derive the masses, sizes and velocity dispersions of 162 spatially resolved GMCs. We perform a detailed study of a subset of 117 GMCs that exhibit simple, single component line profile shapes. Examining the Larson scaling relations for these GMCs we find: 1- a highly correlated mass-size relation in both $^{12}$CO and $^{13}$CO emission; 2- a weakly correlated $^{12}$CO linewidth-size (LWS) relation along with a weaker, almost non-existent, $^{13}$CO LWS relation, suggesting a possible dependence of the LWS relation on spatial scale; and 3-that only 43\% of these GMCs are gravitationally bound. We identify two classes of GMCs based on the strength and extent of their $^{13}$CO emission. Examination of the Larson relations finds that both classes are individually characterized by strong $^{12}$CO mass-size relations and much weaker $^{12}$CO and $^{13}$CO LWS relations. The majority (73\%) of strong $^{13}$CO emitting GMCs are found to be gravitationally bound. However, only 25\% of the weak $^{13}$CO emitting GMCs are bound. The resulting breakdown in the Larson relations in the weak $^{13}$CO emitting population decouples the mass-size and LWS relations demonstrating that independent physical causes are required to understand the origin of each. Finally, in nearly every aspect, the physical properties of the M31 GMCs are found to be very similar to those of local Milky Way clouds.

It has long been accepted that the cosmos determine our personalities, relationships, and even our fate. Unlike our condensed matter colleagues - who regularly use quantum mechanics to determine the healing properties of crystals - astrology techniques have been unchanged since the 19th century. In this paper, we discuss how astrophysical messengers beyond starlight can be used to predict the future and excuse an $\mathcal{O}(1)$ fraction of our negative personality traits.

In this thesis, we examine the interplay of interstellar dust and gas in the Andromeda galaxy (M31). In Chapter 2, we use $^{12}$CO CARMA observations of M31 and dust mass surface density measurements from the Bayesian algorithm PPMAP to investigate whether the dust emissivity index ($\beta$) is different inside and outside molecular clouds. We find little difference between the average $\beta$ inside molecular clouds compared to outside molecular clouds, in disagreement with models which predict an increase of $\beta$ in dense environments. In Chapter 3, we use submillimetre observations of M31 at 450 and 850 $\mu$m from the HASHTAG large programme and present first results of the spatial distribution of dust temperature, $\beta$ and dust mass surface density from this survey. We search for any excess emission from dust at these wavelengths and do not find strong evidence for the presence of a sub-mm excess. In Chapter 4, we produce a new dust-selected cloud catalogue using archival Herschel observations and HASHTAG observations. We show that dust is a good tracer of the ISM gas mass at the scale of individual molecular clouds but with an offset from the combined CO-traced + HI gas masses. In Chapter 5, we measure the star formation efficiency (SFE) of individual clouds, for the clouds extracted in Chapter 4, by using FUV+24 $\mu$m emission to trace both the massive star formation and dust-obscured star formation. We do not find any systematic trends of SFE with radius but do find strong correlations of the star formation rate with atomic gas and molecular gas. We find that SFE is correlated with dust temperature and $\beta$. In Chapter 6, we use a simulated galaxy to test and optimise the Bayesian algorithm PPMAP for application on observations of external galaxies. We find an offset between the input simulation dust mass surface density values and the PPMAP output.

Observations that resolve nearby galaxies into individual regions across multiple phases of the gas-star formation-feedback ``matter cycle'' have provided a sharp new view of molecular clouds, star formation efficiencies, timescales for region evolution, and stellar feedback. We synthesize these results, cover aspects relevant to the interpretation of observables, and conclude that: (1) The observed cloud-scale molecular gas surface density, line width, and internal pressure all reflect the large-scale galactic environment while also appearing mostly consistent with properties of a turbulent medium strongly affected by self-gravity. (2) Cloud-scale data allow for statistical inference of both evolutionary and physical timescales. These suggest that clouds collapse on timescale of order the free-fall or turbulent crossing time ($\sim 10{-}30$~Myr) followed by the formation of massive stars and subsequent rapid ($\lesssim$ 5 Myr) gas clearing. The star formation efficiency per free-fall time is well determined over thousands of regions to be $\epsilon_{\rm ff}\approx 0.5_{-0.3}^{+0.7}\%$. (3) The role of stellar feedback is now measured using multiple observational approaches. The net momentum yield is constrained by the requirement to support the vertical weight of the galaxy disk. Meanwhile, the short gas clearing timescales suggest a large role for pre-supernova feedback in cloud disruption. This leaves the supernovae free to exert a large influence on the larger scale galaxy, including driving turbulence, launching galactic-scale winds, and carving superbubbles.

Cosmic structure on the largest scales preserves the pattern laid down by quantum fluctuations of gravity in the early universe on scales comparable to inflationary horizons. It is proposed here that fluctuations create physical correlations only within finite regions enclosed by causal diamonds, like entanglement in other quantum systems. Conformal geometry is used to calculate a range of angular separation with no causal correlation. Correlations of the cosmic microwave background in this ``causal shadow'' are measured to be three to four orders of magnitude smaller than expected in standard inflation models. It is suggested that this measured symmetry of the primordial pattern signifies a new symmetry of quantum gravity associated with causal horizons.

It is well known that the best way to understand astronomical data is through machine learning, where a "black box" is set up, inside which a kind of artificial intelligence learns how to interpret the features in the data. We suggest that perhaps there may be some merit to a new approach in which humans are used instead of machines to understand the data. This may even apply to fields other than astronomy.

This paper argues why FLAMINGO (Fast Light Atmospheric Monitoring and Imaging Novel Gamma-ray Observatory) is the perfect name for an array of very-high-energy Cherenkov telescopes. Studies which indicate pink is the most suitable pigment for the structures of Cherenkov telescopes have passed with flying colors. Pink optimizes the absorption and reflectivity properties of the telescopes with respect to the characteristic blue color of the Cherenkov radiation emitted by high-energy particles in the atmosphere. In addition to giving the sensitivity a big leg up, a pink color scheme also adds a unique and visually appealing aspect to the project's branding and outreach efforts. FLAMINGO has a fun and memorable quality that can help to increase public engagement and interest in astrophysics and also help to promote diversity in the field with its colorful nature. In an era of increasingly unpronounceable scientific acronyms, we are putting our foot down. FLAMINGO is particularly fitting, as flamingos have eyesight optimized to detect small particles, aligning with the primary purpose of Cherenkov telescopes to detect faint signals from air showers. We should not wait in the wings just wishing for new name to come along: in FLAMINGO we have an acronym that both accurately reflects the science behind Cherenkov telescopes and provides a visually striking identity for the project. While such a sea change will be no easy feet, we are glad to stick our necks out and try: FLAMINGO captures the essence of what an array of Cherenkov telescopes represents and can help to promote the science to a wider audience. We aim to create an experiment and brand that people from all walks of life will flock to.

We explore how the definition of a void influences the conclusions drawn about the impact of the void environment on galactic properties using two void-finding algorithms in the Void Analysis Software Toolkit: V2, a Python implementation of ZOBOV, and VoidFinder, an algorithm which grows and merges spherical void regions. Using the Sloan Digital Sky Survey Data Release 7, we find that galaxies found in VoidFinder voids tend to be bluer, fainter, and have higher (specific) star formation rates than galaxies in denser regions. Conversely, galaxies found in V2 voids show no significant differences when compared to galaxies in denser regions, inconsistent with the large-scale environmental effects on galaxy properties expected from both simulations and previous observations. These results align with previous simulation results that show V2-identified voids "leaking" into the dense walls between voids because their boundaries extend up to the density maxima in the walls. As a result, when using ZOBOV-based void finders, galaxies likely to be part of wall regions are instead classified as void galaxies, a misclassification that can be critical to our understanding of galaxy evolution.

The AMS02 experiment has published the periodic spectra of proton, helium and helium isotopes across the majority of the 24 solar cycle. These precise data exhibit temporal structures that correlate with solar modulation. In this study, we utilize these data to probe three analytic solar modulation models, including the force-field approximation, the convection-diffusion model and the extended force-field approximation with a drift effect. We adopt a method that eliminates the influence of interstellar cosmic ray spectra, and use the Earth-observed spectra at time $t_1$ to predict those at time $t_2$. In order to explore the rigidity-dependence of solar modulation models, we substitute the conventional potential parameter $\phi$ with a modified parameter $\phi'=\frac{R}{ k_2(R)}\phi$ for our analysis. Combining with the $\chi^2$ minimization method, the best-fit modulation parameter $\phi'$ can be evaluated. First, we test the validity of a rigidity-independent $\phi'$ and find that both the force-field approximation (FFA) and the extended force-field approximation (EFFA) agree well with data near the solar minimum period. However, all models significantly deviate from the data during the solar maximum. Consequently, we assume a constant $\phi'(t_1)$ at solar minimum and calculate $\Delta\phi'=\phi'(t_2)-\phi'(t_1)$ for each rigidity bin at time $t_2$. It is found that $\Delta\phi'$ generally adheres to a linear-logarithm relationship with rigidity at any given time. By adopting a linear-logarithm formula of $\Delta\phi'$, we further discover that both the modified FFA and EFFA can reconcile the observations during solar maxima. This suggests that at solar maximum, the parameter $\phi'$, which correlates with the diffusion pattern in the heliospheric magnetic fields, exhibits a rigidity dependence.

Using starlight polarization, we present the properties of foreground dust towards cluster NGC 7380 embedded in H{\sc ii} region Sh 2-142. Observations of starlight polarization are carried out in four filters using an imaging polarimeter equipped with a 104-cm ARIES telescope. Polarization vectors of stars are aligned along the Galactic magnetic field. Towards the east and southeast regions, the dust structure appears much denser than in other regions (inferred from extinction contours and colour composite image) and is also reflected in polarization distribution. We find that the polarization degree and extinction tend to increase with distance and indication for the presence of a dust layer at a distance of around 1.2 $kpc$. We have identified eight potential candidates exhibiting intrinsic polarization by employing three distinct criteria to distinguish between stars of intrinsic polarization and interstellar polarized stars. For interstellar polarized stars, we find that the maximum polarization degree increases with the color excess and has a strong scatter, with the mean value of 1.71$\pm$0.57$\%$. The peak wavelength spans $0.40-0.88\mu$m with the mean value of 0.56$\pm$0.07 $\mu m$, suggesting similar grain sizes in the region as the average diffuse interstellar medium. The polarization efficiency is also found to decrease with visual extinction as $P_{max}/A_{V}\propto A_{V}^{-0.61}$. Our observational results are found to be consistent with the predictions by the radiative torque alignment theory.

Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines.We study several hypotheses that enable robust estimations of the column densities and physical conditions when fitting one or two transitions per molecular species. We study the extent to which simplifying assumptions aimed at reducing the complexity of the problem introduce estimation biases and how to detect them.We focus on the CO and HCO+ isotopologues and analyze maps of a 50 square arcminutes field. We used the RADEX escape probability model to solve the statistical equilibrium equations and compute the emerging line profiles, assuming that all species coexist. Depending on the considered set of species, we also fixed the abundance ratio between some species and explored different values. We proposed a maximum likelihood estimator to infer the physical conditions and considered the effect of both the thermal noise and calibration uncertainty. We analyzed any potential biases induced by model misspecifications by comparing the results on the actual data for several sets of species and confirmed with Monte Carlo simulations. The variance of the estimations and the efficiency of the estimator were studied based on the Cram{\'e}r-Rao lower bound.Column densities can be estimated with 30% accuracy, while the best estimations of the volume density are found to be within a factor of two. Under the chosen model framework, the peak 12CO(1--0) is useful for constraining the kinetic temperature. The thermal pressure is better and more robustly estimated than the volume density and kinetic temperature separately. Analyzing CO and HCO+ isotopologues and fitting the full line profile are recommended practices with respect to detecting possible biases.Combining a non-local thermodynamic equilibrium model with a rigorous analysis of the accuracy allows us to obtain an efficient estimator and identify where the model is misspecified. We note that other combinations of molecular lines could be studied in the future.

The paper proposes a model of deep and prolonged eclipses of young stars of the UX~Ori type. Some of these events continue for decades and existing models cannot explain them. Our paper shows that such eclipses can be caused by the falling of gas and dust clump from the remnants of the protostellar cloud onto the protoplanetary disk. The disturbance in the disk caused by the fall of the clump leads to a surge in the accretion activity of the star and, as a consequence, to an increase in the disk wind. If the circumstellar disk is tilted at a slight angle to the line of sight, then dust raised by the wind from the surface of the disk can cause a strong decrease in the star's brightness, which can last for decades.

We present the results of multicolour $UBVR_{\text{C}}I_{\text{C}}JHK$ photometry, spectroscopic analysis and spectral energy distribution (SED) modelling for the post-AGB candidate IRAS 02143+5852. We detected Cepheid-like light variations with the full peak-to-peak amplitude $\Delta V\sim0.9$ mag and the pulsation period of about 24.9 d. The phased light curves appeared typical for the W Vir Cepheids. The period-luminosity relation for the Type II Cepheids yielded the luminosity $\log L/L_{\odot}\sim2.95$. From a low-resolution spectrum, obtained at maximum brightness, the following atmospheric parameters were determined: $T_\text{eff}\sim7400$ K and $\log g\sim1.38$. This spectrum contains the emission lines H$\alpha$, BaII $\lambda$6496.9, HeI $\lambda$10830 and Pa$\beta$. Spectral monitoring performed in 2019-2021 showed a significant change in the H$\alpha$ profile and appearance of CH and CN molecular bands with pulsation phase. The metal lines are weak. Unlike typical W Vir variables, the star shows a strong excess of infrared radiation associated with the presence of a heavy dust envelope around the star. We modelled the SED using our photometry and archival data from different catalogues and determined the parameters of the circumstellar dust envelope. We conclude that IRAS~02143+5852 is a low-luminosity analogue of dusty RV Tau stars.

We present a Neural Network based emulator for the galaxy redshift-space power spectrum that enables several orders of magnitude acceleration in the galaxy clustering parameter inference, while preserving 3$\sigma$ accuracy better than 0.5\% up to $k_{\mathrm{max}}$=0.25$h^{-1}Mpc$ within $\Lambda$CDM and around 0.5\% $w_0$-$w_a$CDM. Our surrogate model only emulates the galaxy bias-invariant terms of 1-loop perturbation theory predictions, these terms are then combined analytically with galaxy bias terms, counter-terms and stochastic terms in order to obtain the non-linear redshift space galaxy power spectrum. This allows us to avoid any galaxy bias prescription in the training of the emulator, which makes it more flexible. Moreover, we include the redshift $z \in [0,1.4]$ in the training which further avoids the need for re-training the emulator. We showcase the performance of the emulator in recovering the cosmological parameters of $\Lambda$CDM by analysing the suite of 25 AbacusSummit simulations that mimic the DESI Luminous Red Galaxies at $z=0.5$ and $z=0.8$, together as the Emission Line Galaxies at $z=0.8$. We obtain similar performance in all cases, demonstrating the reliability of the emulator for any galaxy sample at any redshift in $0 < z < 1.4$

We investigate the physical origins of the Balmer decrement anomalies in GS-NDG-9422 (Cameron et al. 2023) and RXCJ2248-ID (Topping et al. 2024) galaxies at $z\sim 6$ whose $\mathrm{H}\alpha/\mathrm{H}\beta$ values are significantly smaller than $2.7$, the latter of which also shows anomalous $\mathrm{H}\gamma/\mathrm{H}\beta$ and $\mathrm{H}\delta/\mathrm{H}\beta$ values beyond the errors. Because the anomalous Balmer decrements are not reproduced under the Case B recombination, we explore the nebulae with the optical depths smaller and larger than the Case B recombination by physical modeling. We find two cases quantitatively explaining the anomalies; 1) density-bounded nebulae that are opaque only up to around Ly$\gamma$-Ly8 transitions and 2) ionization-bounded nebulae partly/fully surrounded by optically-thick excited H{\sc i} clouds. The case of 1) produces more H$\beta$ photons via Ly$\gamma$ absorption in the nebulae, requiring fine tuning in optical depth values, while this case helps ionizing photon escape for cosmic reionization. The case of 2) needs the optically-thick excited H{\sc i} clouds with $N_2\simeq 10^{12}-10^{13}$ $\mathrm{cm^{-2}}$, where $N_2$ is the column density of the hydrogen atom with the principal quantum number of $n=2$. Interestingly, the high $N_2$ values qualitatively agree with the recent claims for GS-NDG-9422 with the strong nebular continuum requiring a number of $2s$-state electrons and for RXCJ2248-ID with the dense ionized regions likely coexisting with the optically-thick clouds. While the physical origin of the optically-thick excited H{\sc i} clouds is unclear, these results may suggest gas clouds with excessive collisional excitation caused by an amount of accretion and supernovae in the high-$z$ galaxies.

The cosmic microwave background (CMB) radiation offers a unique avenue for exploring the early Universe's dynamics and evolution. In this paper, we delve into the fascinating realm of slow-roll inflation, contextualizing the primordial acoustic perturbations as the resonant echoes akin to the iconic sound of Chewbacca from the Star Wars universe. By extrapolating polynomial potentials for these primordial sounds, we illuminate their role in shaping the inflationary landscape. Leveraging this framework, we calculate the scalar spectral index ($n_s$) and tensor-to-scalar ratio ($r$), providing insights into the underlying physics governing the inflationary epoch. Employing a rigorous chi-square ($\chi^2$) analysis, we meticulously scrutinize the Planck data combined with that offered by the BICEP/Keck collaboration to identify the Chewbacca sound profile that best aligns with observational constraints. Our findings not only shed light on the intricate interplay between sound and cosmology but also unveil intriguing parallels between the cosmic symphony of the early universe and beloved cultural icons.

In recent years the James Webb Space Telescope has enabled the frontier of observational galaxy formation to push to ever higher redshift, deep within cosmic dawn. However, what is high-redshift, and when was cosmic dawn? While widely used, these terms (as well as many other confusing terms) are not consistently defined in the literature; this both hampers effective communication but also impedes our ability to precisely characterize and understand the phenomena under investigation. In this article we seek to address this issue of utmost importance. We begin by definitively defining terms such as ``high-redshift'', ``cosmic dawn'', etc. However, despite the rigorous definitions for them we present, both the adjective-based redshift and diurnal marker (time-of-day) division schemes suffer from issues including not being sufficiently granular, angering cosmologists, being arbitrary, and having a geocentric bias. To overcome these we introduce the \textit{redshiFt epOchs fOr everyboDy} (FOOD) framework, a revolutionary new division scheme based on eating occasions, i.e. meals.

We present the third catalog release of the wide-area (31.3 deg$^2$) Stripe 82 X-ray survey. This catalog combines previously published X-ray source properties with multiwavelength counterparts and photometric redshifts, presents 343 new spectroscopic redshifts, and provides black hole masses for 1396 Type 1 Active Galactic Nuclei (AGN). With spectroscopic redshifts for 3457 out of 6181 Stripe 82X sources, the survey has a spectroscopic completeness of 56%. This completeness rises to 90% when considering the contiguous portions of the Stripe 82X survey with homogeneous X-ray coverage at an optical magnitude limit of $r<22$. Within that portion of the survey, 23% of AGN can be considered obscured by being either a Type 2 AGN, reddened ($R-K > 4$, Vega), or X-ray obscured with a column density $N_{\rm H} > 10^{22}$ cm$^{-2}$. Unlike other surveys, there is only a 18% overlap between Type 2 and X-ray obscured AGN. We calculated black hole masses for Type 1 AGN that have SDSS spectra using virial mass estimators calibrated on the H$\beta$, MgII, H$\alpha$, and CIV emission lines. We find systematic differences in these black hole mass estimates, indicating that statiscal analyses should use black hole masses calculated from the same formula to minimize systematic bias. We find that the highest luminosity AGN are accreting at the highest Eddington ratios, consistent with the picture that most mass accretion happens in the phase when the AGN is luminous ($L_{\rm 2-10 keV} > 10^{45}$ erg s$^{-1}$).

A Total Solar Eclipse (TSE) is a shocking and sublime experience. In just a week hundreds of millions of Homo Sapiens will attempt to see the 2024 eclipse as it stretches across the North American continent. However, while Homo Sapiens may be uniquely positioned to understand and predict eclipses, they are not the only species capable of observing them. The precise alignment of the Moon, Earth and Sun all existed well before humans. In the same way we share this planet capable of hosting life, the fantastic astronomical experiences available on it are not exclusive either. We present a framework to calculate the number of Total Solar Eclipses experienced by a species at any point in Earth's history. This includes factoring in the evolution of the Sun-Moon-Earth system, the duration the species is extant, and average population. We normalize over the geographic range by calculating an Astronomical World Eclipse Surface cOverage MEtric (AWESOME) time. To illustrate this framework we look at the case study of the family Limulidae (Horseshoe Crabs) and estimate the number of individuals that have seen an eclipse. We compare it to the number of current Homo Sapiens that view eclipses, and predict if it is possible for another species to take the ''top'' spot before the final total solar eclipse in ~ 380 million years.

Large surveys provide numerous non-targeted observations of small bodies (SSOs). The upcoming LSST of the Rubin observatory will be the largest source of SSO photometry in the next decade. With non-coordinated epochs of observation, colors, and therefore taxonomy and composition, can only be computed by comparing absolute magnitudes obtained in each filter by solving the phase function (evolution of brightness of the small body against the solar phase angle). Current models in use in the community (HG, HG12* , HG1G2) however fail to reproduce the long-term photometry of many targets due to the change in aspect angle between apparitions. We aim at deriving a generic yet simple phase function model accounting for the variable geometry of the SSOs over multiple apparitions. We propose the sHG1G2 phase function model in which we introduce a term describing the brightness changes due to spin orientation and polar oblateness. We apply this new model to 13,245,908 observations of 122,675 SSOs. These observations were acquired in the g and r filters with the Zwicky Transient Facility. We retrieve them and implement the new sHG1G2 model in Fink, a broker of alerts designed for the LSST. The sHG1G2 model leads to smaller residuals than other phase function models, providing a better description of the photometry of asteroids. We determine the absolute magnitude H and phase function coefficients (G1, G2) in each filter, the spin orientation (RA_0,DEC_0), and the polar-to-equatorial oblateness R for 95,593 Solar System Objects (SSOs), which constitutes about a tenfold increase in the number of characterised objects compared to current census. The application of the sHG1G2 model on ZTF alert data using the FINK broker shows that the model is appropriate to extract physical properties of asteroids from multi-band and sparse photometry, such as the forthcoming LSST survey.

Finding a suitable very long baseline (VLBI) interferometer geometry is a key task in planning observations, especially imaging sessions. The main characteristic of the quality of VLBI imaging data is the (u, v)-coverage. In the case when one or more radio telescopes are located in space, this task becomes more complex. This paper presents a method for recovering the optimal orbital parameters of space radio telescopes for a given desired (u, v)-coverage, which in turn is the inverse task of searching for the optimal geometry and orbital configurations of space-ground and pure space VLBI interferometers.

Recently, cosmology has seen a surge in alternative models that purport to solve the discrepancy between the values of the Hubble constant $H_0$ as measured by cosmological microwave background anisotropies and local supernovae, respectively. In particular, many of the most successful approaches have involved varying fundamental constants, such as an alternative value of the fine structure constant and time-varying values of the electron mass, the latter of which showed particular promise as the strongest candidate in several earlier studies. Inspired by these approaches, in this paper, we investigate a cosmological model where the value of the geometric constant $\pi$ is taken to be a free model parameter. Using the latest CMB data from Planck as well as baryon-acoustic oscillation data, we constrain the parameters of the model and find a strong correlation between $\pi$ and $H_0$, with the final constraint $H_0 = 71.3 \pm 1.1 \ \mathrm{ km/s/Mpc}$, equivalent to a mere $1.5\sigma$ discrepancy with the value measured by the SH0ES collaboration. Furthermore, our results show that $\pi = 3.206 \pm 0.038$ at $95 \%$ C.L., which is in good agreement with several external measurements discussed in the paper. Hence, we conclude that the $\pi \Lambda$CDM model presented in this paper, which has only a single extra parameter, currently stands as the perhaps strongest solution to the Hubble tension.

Over the past decade, exoplanet atmospheric characterization has became what some might call the cosmology of astronomy. In an attempt to extract and understand the weak planetary signals (a few percent down to a few tens of ppm times that of their host-star signals), researchers have developed dozens of idealized planetary atmospheric models. Physical interpretations hinge on pretending that we understand stellar signals (as well behaved mostly temporarily static spherical cows), as well as planetary signals (as unidimensional objects, or sometimes quasi-multidimensional objects). The discovery of small and cool planets has lead to analyze planetary signals well below the designed photometric precision of current instrumentation. The challenge is up there, and keep us busy, so all is well. Here we present yet another open-source tool to analyze exoplanet data of time-series observations. The {\puppies} code is available via PyPI (\texttt{pip install exo-puppies}) and conda, the documentation is located at https://puppies.rtfd.io

Accurate age and mass determinations for young pre-main sequence stars are made challenging by the presence of large-scale starspots. We present results from a near-infrared spectroscopic survey of ten T-Tauri Stars in Taurus-Auriga that characterize spot filling factors and temperatures, the resulting effects on temperature and luminosity determinations, and the consequences for inferred stellar masses and ages. We constructed composite models of spotted stars by combining BTSettl-CIFIST synthetic spectra of atmospheres to represent the spots and the photosphere along with continuum emission from a warm inner disk. Using a Markov-Chain Monte-Carlo algorithm, we find the best-fit spot and photospheric temperatures, spot filling factors, as well as disk filling factors. This methodology allowed us to reproduce the 0.75-2.40 micron stellar spectra and molecular feature strengths for all of our targets, disentangling the complicated multi-component emission. For a subset of stars with multi-epoch observations spanning an entire stellar rotation, we correlate the spectral variability and changes in the filling factors with rotational periods observed in K2 and AAVSO photometry. Combining spot-corrected effective temperatures and Gaia distances, we calculate luminosities and use the Stellar Parameters of Tracks with Starspots (SPOTS) models to infer spot-corrected masses and ages for our sample of stars. Our method of accounting for spots results in an average increase of 60% in mass and a doubling in age with respect to traditional methods using optical spectra that do not account for the effect of spots.

In the seven years that the starship Voyager spent in the Delta Quadrant, it used many questionable techniques to engage with alien civilizations and ultimately find its way home. From detailed studies of their logs and opening credits, we simulate Voyager's practice of orbiting a planet, to examine the effect on planetary rings. We outline a feasible planetary system and simulate the extent to which its rings would be disrupted. We find that Voyager's orbit could inflate the height of the rings in the vicinity of the spacecraft by a factor of 2, as well as increase the relative speeds of neighboring planetesimals within the rings. This increase in ring thickness has the potential to alter shadows on any moons of this planet, impacting ring-shadow based religions. Additionally, the acceleration of these planetesimals could rival their gravity, bucking any alien inhabitants and their tiny civilizations off of their planetesimal homeworlds. Finally, we posit that due to increased collisions amongst the planetesimals (which may harbor tiny intelligent life) the trajectory of these civilizations may be forever altered, violating the prime directive.

The number of planets in the solar system over the last three centuries has, perhaps surprisingly, been less of a fixed value than one would think it should be. In this paper, we look at the specific case of Vulcan, which was both a planet before Pluto was a planet and discarded from being a planet before Pluto was downgraded. We examine the historical context that led to its discovery in the 19th century, the decades of observations that were taken of it, and its eventual fall from glory. By applying a more modern understanding of astrophysics, we provide multiple mechanisms that may have changed the orbit of Vulcan sufficiently that it would have been outside the footprint of early 20th century searches for it. Finally, we discuss how the April 8, 2024 eclipse provides a renewed opportunity to rediscover this lost planet after more than a century of having been overlooked.

The super-Earth LHS 1140 b is an interesting target for atmospheric observations since it is close to the habitable zone of its star and falls in the gap of the radius distribution of small exoplanets, in the region thought to correspond to the transition between planets with and without atmospheres. Observations of the primary transit with WFC3 on board of the Hubble Space Telescope (HST) revealed a modulation in the planet transmission spectrum compatible with the presence of water; however this modulation may be also due to stellar activity-related phenomena. Here we present a detailed analysis of the WFC3/HST observations to probe the nature of this modulation and to understand if it can be attributable to the presence of unocculted spots on the stellar surface. Our analysis strongly suggests that LHS1140 is a rather quiet star with subsolar [Fe/H] and enriched in alpha elements. Therefore, we rule out the possibility that the planetary spectrum is affected by the presence of spots and faculae. This analysis shows the importance of a proper modelling of the stellar spectrum when analyzing transit observations. Finally, we modelled the planetary atmosphere of LHS1140 b to retrieve its atmospheric composition. However, the low resolution and the narrow spectral range of HST observations prevented us from definitively determining whether the spectral features are attributable to the presence of water or of other molecules in the planetary atmosphere.

Context. Understanding the Milky Way's formation and evolution across cosmic epochs necessitates precise stellar age determination across all Galactic components. Recent advancements in asteroseismology, spectroscopy, stellar modelling, and machine learning, coupled with all-sky surveys, now offer highly reliable stellar age estimates. Aims. This study aims to furnish accurate age assessments for the Main Red Star Sample within the APOGEE DR17 catalogue. Leveraging asteroseismic age constraints, we employ machine learning to achieve this goal. Methods. We explore optimal non-asteroseismic stellar parameters, including T$_{eff}$, L, [CI/N], [Mg/Ce], [$\alpha$/Fe], U(LSR) velocity, and 'Z' vertical height from the Galactic plane, to predict ages via categorical gradient boost decision trees. Training merges samples from the TESS Southern Continuous Viewing Zone and Second APOKASC catalogue to mitigate data shifts, enhancing prediction reliability. Validation employs an independent dataset from the K2 Galactic Archaeology Program. Results. Our model yields a median fractional age error of 20.8%, with a prediction variance of 4.77%. Median fractional errors for stars older than 3 Gyr range from 7% to 23%, from 1 to 3 Gyr range from 26% to 28%, and for stars younger than 1 Gyr, it's 43%. Applicable to 125,445 stars in the APOGEE DR17 Main Red Star Sample, our analysis confirms previous findings on the young Galactic disc's flaring and reveals an age gradient among the youngest Galactic plane stars. Additionally, we identify two groups of metal-poor ([Fe/H] < -1 dex) young stars (Age < 2 Gyr) exhibiting similar chemical abundances and halo kinematics, likely remnants of the predicted third gas infall episode (~2.7 Gyr ago).

We present a new standard acronym for Active Galactic Nuclei, finally settling the argument of AGN vs. AGNs. Our new standard is not only etymologically superior (following the consensus set by SNe), but also boasts other linguistic opportunities, connecting strongly with relevant theology and streamlining descriptions of AGN properties.

We aim at facilitating the visualization of astrophysical data for several tasks, such as uncovering patterns, presenting results to the community, and facilitating the understanding of complex physical relationships to the public. We present pastamarkers, a customized Python package fully compatible with matplotlib, that contains unique pasta-shaped markers meant to enhance the visualization of astrophysical data. We prove that using different pasta types as markers can improve the clarity of astrophysical plots by reproducing some of the most famous plots in the literature.

The baryonic feedback effect is considered as a possible solution to the so-called $S_8$ tension indicated in cosmic shear cosmology. The baryonic effect is more significant on smaller scales, and affects the cosmic shear two-point correlation functions (2PCFs) with different scale- and redshift-dependencies from those of the cosmological parameters. In this paper, we use the Hyper Suprime-Cam Year 3 (HSC-Y3) data to measure the cosmic shear 2PCFs ($\xi_{\pm}$) down to 0.28 arcminutes, taking full advantage of the high number density of source galaxies in the deep HSC data, to explore a possible signature of the baryonic effect. While the published HSC analysis used the cosmic shear 2PCFs on angular scales, which are sensitive to the matter power spectrum at $k\lesssim 1~h{\rm Mpc}^{-1}$, the smaller scale HSC cosmic shear signal allows us to probe the signature of matter power spectrum up to $k\simeq 20~h{\rm Mpc}^{-1}$. Using the accurate emulator of the nonlinear matter power spectrum, DarkEmulator2, we show that the dark matter-only model can provide an acceptable fit to the HSC-Y3 2PCFs down to the smallest scales. In other words, we do not find any clear signature of the baryonic effects or do not find a systematic shift in the $S_8$ value with the inclusion of the smaller-scale information as would be expected if the baryonic effect is significant. Alternatively, we use a flexible 6-parameter model of the baryonic effects, which can lead to both enhancement and suppression in the matter power spectrum compared to the dark matter-only model, to perform the parameter inference of the HSC-Y3 2PCFs. We find that the small-scale HSC data allow only a fractional suppression of up to 5 percent in the matter power spectrum at $k\sim 1~h{\rm Mpc}^{-1}$, which is not sufficient to reconcile the $S_8$ tension.

Multi-reference configuration interaction (MRCI) potential energy curves (PECs) and spin-orbit couplings for the X $^2\Pi$, A $^2 \Sigma^+$, 1 $^2 \Sigma^-$, 1 $^4 \Sigma^-$, and 1 $^4 \Pi$ states of OH are computed and refined against empirical energy levels and transitions to produce a spectroscopic model. Predissociation lifetimes are determined by discretising continuum states in the variational method nuclear motion calculation by restricting the calculation to finite range of internuclear separations. Varying this range give a series of avoided crossings between quasi-bound states associated with the A $^2 \Sigma^+$ and continuum states, from which predissociation lifetimes are extracted. 424 quasi-bound A $^2 \Sigma^+$ state rovibronic energy levels are analysed and 374 predissociation lifetimes are produced, offering good coverage of the predissociation region. Agreement with measured lifetimes is satisfactory and a majority of computed results were within experimental uncertainty. A previously unreported A $^2 \Sigma^+$ state predissociation channel which goes via the X $^2\Pi$ is identified in the calculations. A python package, binslt, is produced to calculate predissociation lifetimes, associated line broadening parameters, and uncertainties from Duo *.states files is made available. The PECs and other curves from this work will be used to produce a rovibronic ExoMol linelist and temperature-dependent photodissociation cross sections for the hydroxyl radical.

EUropean Heliospheric FORecasting Information Asset (EUHFORIA) is a physics-based data-driven solar wind and CME propagation model designed for space weather forecasting and event analysis investigations. Although EUHFORIA can predict the solar wind plasma and magnetic field properties at Earth, it is not equipped to quantify the geoeffectiveness of the solar transients in terms of the geomagnetic indices like the disturbance storm time (Dst) index and the eauroral indices that quantify the impact of the magnetized plasma encounters on Earth's magnetosphere. Therefore, we couple EUHFORIA with the Open Geospace General Circulation Model (OpenGGCM), a magnetohydrodynamic model of the response of Earth's magnetosphere, ionosphere, and thermosphere, to transient solar wind characteristics. In this coupling, OpenGGCM is driven by the solar wind and interplanetary magnetic field obtained from EUHFORIA simulations to produce the magnetospheric and ionospheric response to the CMEs. This coupling is validated with two observed geoeffective CME events driven with the spheromak flux-rope CME model. We compare these simulation results with the indices obtained from OpenGGCM simulations driven by the measured solar wind data from spacecraft. We further employ the dynamic time warping (DTW) technique to assess the model performance in predicting Dst. The main highlight of this study is to use EUHFORIA simulated time series to predict the Dst and auroral indices 1 to 2 days in advance, as compared to using the observed solar wind data at L1, which only provides predictions 1 to 2 hours before the actual impact.

We introduce a machine learning-based method for extracting HI sources from 3D spectral data, and construct a dedicated dataset of HI sources from CRAFTS. Our custom dataset provides comprehensive resources for HI source detection. Utilizing the 3D-Unet segmentation architecture, our method reliably identifies and segments HI sources, achieving notable performance metrics with recall rates reaching 91.6% and accuracy levels at 95.7%. These outcomes substantiate the value of our custom dataset and the efficacy of our proposed network in identifying HI source. Our code is publicly available at https://github.com/fishszh/HISF.

Local and distant measurements of the Hubble constant are in significant tension: local measurements of the Hubble constant appear to show a Universe that is significantly contracted when compared to distant measurements. From the point of view of an observer, a passing gravitational wave could cause the Universe to appear locally contracted and expanded in a quadrupolar pattern. The inspiral of a pair of stupendously large black holes (SLABs) with a chirp mass of $\sim10^{21}~\rm{M}_\odot$ may produce gravitational radiation with sufficiently large amplitude and wavelength to increase $H_0$ in one direction, and decrease it by the same amount in the other. These tensions would then oscillate with a period corresponding to half the orbital period of the binary. If such a gravitational wave were aligned with the plane of the Milky Way, most readily visible galaxies would appear closer than they actually are, thereby causing the apparent Hubble tension. Due to the long binary period, we would be in the same phase of the gravitational wave for the complete history of astronomical observation. The opposite tension would be visible in the orthogonal directions, thus giving the opportunity to falsify the existence of inspiraling SLAB binaries. As a corollary, the Hubble tension may place an upper limit on the maximum mass of inspiraling black holes in the Universe.

The Arago spot is an intensity maximum at the center of a shadow created by constructive interference of diffracted waves around a spherical object. While the study of diffraction patterns usually concerns visible light, de Broglie's wave nature of matter makes diffraction theory applicable for particles, such as neutrinos, as well. During a solar eclipse, some of the neutrinos emitted by the Sun are diffracted by the Moon, resulting in a diffraction pattern that can be observed on Earth. In this paper we consider the theoretically emerging solar neutrino Arago spot as a means to measure the location of the Moon with high accuracy and consider its implication on the orbit of the Moon given Heisenberg's uncertainty principle. Our results indicate that the Moon is not at immediate risk of orbital decoupling due to the observation of a solar neutrino Arago spot.